The present invention relates to aerosol delivery of medication to the lungs and more particularly, the present invention relates to delivery systems for application of nebulized medication to the lungs with improved delivery rates, efficiencies, and control.
Many types of medication can be administered to a patient via the respiratory tract. Medication delivered through the respiratory tract may be carried with a patient""s inhalation breath as airborne particles (e.g. an aerosol or nebula) into the lungs where the medication can cross through the thin membrane of the alveoli and enter the patient""s bloodstream. Delivery of medication via the respiratory tract may be preferred in many circumstances because medication delivered this way enters the bloodstream very rapidly. Delivery of medication to the lungs may also be preferred when the medication is used in a treatment of a disease or condition affecting the lungs in order to apply or target the medication as close as physically possible to the diseased area.
Although delivery of medication via the respiratory tract has been used for many years, there are difficulties associated with prior systems that have limited their use and application. For example, conventional methods have provided for only limited medication delivery rates, efficiency, and control. Conventional methods for aerosol delivery result in a substantial portion of the medicine failing to be delivered to the lungs, and thereby possibly being wasted, or possibly being delivered to other parts of the body, e.g. the trachea.
Aerosols in general are relatively short-lived and can settle out into larger particles or droplets relatively quickly. Aerosols can also impact each other or other objects, settle out as sediment, diffuse, or coalesce. Aerosol particles can also be subject to hydroscopic growth as they travel. Delivery of medicine as airborne particles requires conversion of the medicine, which may be in liquid form, to an aerosol followed relatively quickly by application of the aerosol to the respiratory tract. One such device that has been utilized for this purpose is an inhaler. Inhalers may atomize a liquid to form an aerosol which a person inhales via the mouth or nose. Inhalers typically provide only limited delivery of medication to the lungs since most of the medication is deposited on the linings of the respiratory tract. It is estimated that as little as 10-15% of an aerosol inhaled in this way reaches the alveoli.
Aerosol delivery of a medication to a patient""s respiratory tract also may be performed while the patient is intubated, i.e. when an endotracheal tube is positioned in the patient""s trachea to assist in breathing. When an endotracheal tube is positioned in a patient, a proximal end of the endotracheal tube may be connected to a mechanical ventilator and the distal end is located in the trachea. An aerosol may be added to the airflow in the ventilator circuit of the endotracheal tube and carried by the patient""s inhalation to the lungs. A significant amount of the aerosolized medication may be deposited inside the endotracheal tube and the delivery rate of the medicine to the lungs also remains relatively low and unpredictable.
The low and unpredictable delivery rates of prior aerosol delivery systems have limited the types of medications that are delivered via the respiratory tract. For new medications that are relatively expensive, the amount of wasted medicine may be a significant cost factor in the price of the therapy. Therefore, it would be advantageous to increase the delivery rate or efficiency of a medicine delivered to the lungs.
Another consideration is that some aerosols delivered to the lungs may have adverse side effects, e.g. radioactive tracers used for lung scans. Therefore, it would be advantageous to minimize the overall amount of medication delivered while maintaining the efficacy of the medication by providing the same or a greater amount of the medication to the desired site in the respiratory tract.
Further, some medications may be more effective when delivered in certain particle sizes. Accordingly, an improved aerosol delivery system may provide for improved rates and efficiencies of delivery also taking into account the aerosol particle size.
It may also be important to administer certain medications in specific, controlled dosages. The prior methods of aerosol delivery not only were inefficient, but also did not provide a reliable means to control precisely the dosage being delivered.
It may also be advantageous to be able to target medication to a specific bronchus, or specific groups of bronchia, as desired, while avoiding delivery of medication to other portions of the lungs.
Taking into account these and other considerations, aerosol delivery via the respiratory tract could become an even more widely used and effective means of medication delivery if the delivery rate and efficiency of the delivery could be improved.
According to an aspect of the present invention, there is provided a method and apparatus for delivering a drug with control and efficiency to a patient via the patient""s respiratory system. A nebulization catheter is positioned in the patient""s respiratory system so that a distal end of the nebulization catheter is in the respiratory system and a proximal end is outside the body. According to a first aspect, the nebulization catheter may be used in conjunction with an endotracheal tube and preferably is removable from the endotracheal tube. The nebulization catheter conveys medicine in liquid form to the distal end at which location the medicine is nebulized by a pressurized gas or other nebulizing agent. The nebulized medicine is conveyed to the patient""s lungs by the patient""s respiration which may be assisted by a ventilator. The nebulizing catheter incorporates alternative constructions taking into account anatomical considerations and the properties of the medicine being nebulized to provide delivery of medicine with control and efficiency.